Fiber optic sensor assembly for sensor delivery device

ABSTRACT

Methods and sensor delivery devices for monitoring a fluid pressure within a vascular structure, the devices including an elongated sheath sized for sliding along a guidewire, a sensor assembly including a fiber optic sensor, a housing surrounding the sensor, a first cavity between the distal end of the sensor and a distal aperture of the housing, a filler extending from at least the distal end of the housing distally and tapering inward toward the outer surface of the sheath, a second cavity in the filler with an opening at the outer surface of the filler and adjoining the distal aperture of the housing, and an optical fiber. The sensor delivery device may also include an outer layer that partially covers the second cavity with an aperture over the opening of the second cavity.

PRIORITY

This application claims priority to U.S. Pat. App. No. 61/673,840 filedJul. 20, 2012 and entitled Fiber Optic Sensor Assembly for SensorDelivery Device, the disclosure of which is incorporated by reference.

TECHNICAL FIELD

The present application relates to the field of medical devicetechnology and, more particularly, to pressure sensors for measuringfluid pressure in anatomical (e.g., vascular) structures of patients,such as in blood vessels or across heart valves.

BACKGROUND

When pressure measurements are made within a human or animal, such aswithin the vascular system, the physical characteristics of theenvironment make obtaining accurate measurements more complicated thanother fluid pressure measurements. For example, such sensors aregenerally non-toxic and small, in order to cause as little trauma to theindividual as possible. In many cases, it may be necessary for themeasuring device to enter the body in one location but to make thepressure measurement in a different location which may be a significantdistance away from the point of entry of the device. It may therefore benecessary to deliver the sensor to the location using a delivery devicesuch as a catheter. Such a pressure sensing device must therefore becapable of being transported to a different location using a deliverydevice and must further be able to transmit data back out of the body.Finally, when the pressure measurements are made within the arterialsystem, the pressure is not steady but rather is pulsatile, rising andfalling to an upper systolic and lower diastolic pressure with eachheartbeat, adding further complexity to the pressure measurementprocess.

For some patients, it is useful to obtain a pressure measurement withinthe coronary arteries. In particular, when a sclerotic lesion is presentwithin the coronary arteries, pressure measurements made upstream anddownstream of the lesion can be used to determine whether or not anintervention, such as angioplasty or stent placement, is required.Because such measurements may be used as a basis for therapy decisions,it is important that they be accurate. However, the very small size ofthe coronary arteries, which may be about 2 mm, and which may be furthernarrowed by sclerotic lesions or complicated by the presence of stents,as well as the pulsatile nature of the blood flow, and the need to avoidcausing any trauma to these critical vessels, present challenges todesigning pressure sensing systems.

SUMMARY

Various embodiments of the invention are described and shown herein. Inone embodiment, a sensor delivery device may be used for monitoring afluid pressure within a vascular structure of a patient, such as withinthe coronary arteries. The sensor delivery device may include anelongated tubular sheath sized for sliding along a guidewire and havingan outer surface and a sensor assembly. The sensor assembly may includea fiber optic sensor such as a pressure sensor, a housing surroundingthe sensor, the housing having a proximal end with a proximal aperture,a distal end with a distal aperture, an inner surface adjoined to theouter surface of the sheath, and an outer surface opposing the innersurface. The sensor assembly may also include a first cavity between thedistal end of the sensor and the distal aperture of the housing, afiller extending from at least the distal end and outer surface of thehousing distally with an outer surface that tapers inward toward theouter surface of the sheath as the filler extends distally, and a secondcavity in the filler. The second cavity may include an opening at theouter surface of the filler and may adjoin the distal aperture of thehousing. The opening and apertures are generally useful for providingfluid communication between the sensor and a patient. The sensordelivery device may further include an optical fiber extending along theouter surface of the sheath, passing through the proximal aperture ofthe housing and adjoined to the sensor at a distal end of the opticalfiber. In some embodiments, the sensor delivery device may also includean outer layer overlying the filler and comprising an aperture. Theouter layer may partially cover the second cavity and the aperture mayoverlie the opening of the second aperture. In some embodiments, theouter layer may encircle the sensor assembly, the sheath, and theoptical fiber.

The outer surface of the sheath may form a bottom of the second cavity,the distal end of the housing may form a proximal end of the cavity, thefiller material itself may form the distal end of the second cavity andthe opposing side surfaces of the second cavity, and the outer layerforms a top of the second cavity.

In some embodiments, the filler surrounds all of the housing except thebottom surface of the housing which abuts the sheath. In someembodiments, the filler may extend proximally from the proximal end andouter surface of the housing and taper inwardly toward the outer surfaceof the sheath as it extends proximally.

In some embodiments, the second cavity has a length from a proximal to adistal end of the second cavity which is greater than a length of theouter layer aperture from a proximal to a distal end of the outer layeraperture. In some embodiments, the outer layer aperture may have an areaof between about 0.05 and about 0.5 mm². In some embodiments, the secondcavity may have a volume of between about 0.04 and about 0.12 mm³.

The sheath of the sensor delivery device may include a distal sleeve anda proximal portion adjoined to the distal sleeve, with the optical fiberextending within the proximal portion and with the proximal portionconfigured to be separate from the guidewire.

Various embodiments also include methods of measuring the intravascularpressure of a patient at a location of interest using any of the sensordelivery devices described above. The method may include inserting thesensor delivery device into the patient's vasculature, advancing thesensor delivery device to the location of interest; and measuring theintravascular pressure at the location of interest using the pressuresensor.

The details of one or more embodiments are set forth in the accompanyingdrawing figures and the description below. Other features, objects, andadvantages will be apparent from the description and attachments. Theembodiments shown and described are provided for the purposes ofillustration, not limitation.

FIGURES

FIG. 1 is a side plan with portions rendered transparent of a sensordelivery device including a sensor assembly according to variousembodiments;

FIG. 2 is a side plan with portions rendered transparent of a portion ofthe sensor delivery device of FIG. 1 including the sensor assembly;

FIG. 3 is a longitudinal cross sectional view of a portion of the sensorassembly of FIG. 2;

FIG. 4 is an axial cross sectional view of the sensor delivery device ofFIG. 1 proximal to the sensor assembly;

FIG. 5 is an axial cross sectional view of the sensor delivery device ofFIG. 1 throughout the sensor assembly; and

FIG. 6 is a schematic view of a contrast injection system for use withsensor delivery device and a sensor assembly according to variousembodiments.

DETAILED DESCRIPTION

The following detailed description should be read with reference to theaccompanying drawings, in which like numerals denote like elements. Thedrawings, which are not necessarily to scale, depict selectedembodiments—other possible embodiments may become readily apparent tothose of ordinary skill in the art with the benefit of these teachings.Thus, the embodiments shown in the accompanying drawings and describedbelow are provided for illustrative purposes, and are not intended tolimit the scope as called for in the claims appended hereto. Variousexemplary embodiments are described herein with reference to theaccompanying drawing figures in which like numbers describe likeelements. References to above, below, horizontal, vertical, front, back,left, right and the like shall refer to the orientation of the devicewhen it is properly positioned during use.

Various embodiments may be used to measure blood pressure within thecoronary arteries of a patient. Such measurements can be used to measurearterial pressure upstream and downstream of a stenotic lesion or otherarterial narrowing (such as narrowing due to the presence of a stent),for example, to assess the severity of the condition and to assist inmaking therapy decisions. Alternatively, various embodiments may be usedto assess heart valves or to measure pressure or pressure gradientsperipherally within the peripheral vessels, for example.

Fiber optic pressure sensors useful in various embodiments may bedelivered to a location of interest using a guidewire based deliverysystem, for example. One example of such a system is sometimes referredto as a monorail or rapid exchange system. The fiber optic sensor may beused with the monorail pressure system or any other monorail, rapidexchange catheter or any over-the-wire style catheter and may betransported to a location of interest on a distal sleeve. In someembodiments, the sensor is encased within a housing that is furthersurrounded by a filler, and these elements together form a sensorassembly. The housing may be stainless steel, polyimide or otherappropriate material. The housing may be elongated, having a proximalend and a distal end. An optical fiber may extend proximally from thesensor and exit the housing through a proximal aperture in the proximalend of the housing. The housing may also include a distal aperture. Insome embodiments, the distal aperture is in the distal end of thehousing and is aligned with the diaphragm of the pressure sensor, with aspace forming a first cavity between the distal aperture and the sensor.

Because the sensor delivery system may traverse the coronary arteries,various embodiments include a filler to form a tapered distal surface ofthe sensor assembly. In some embodiments, the filler portion of thesensor assembly tapers inward as it extends distally from the housing intoward the distal sleeve on which it is carried, being thinnest at itsdistal end. By tapering in this way, the sensor assembly avoids having ablunt end, perpendicular to the guidewire (and therefore alsoperpendicular to the direction of motion of the distal sleeve), whichcould make it difficult to advance through narrowed portions of thecoronary arteries. In order to allow pressure to be effectivelytransferred from the surrounding fluid to the sensor, the filler mayinclude a cavity which forms the second cavity (the first cavity beingwithin the housing), located proximal to the proximal aperture of thehousing. The second cavity is open at the outer surface of the filler.In this way, pressure is transmitted through the opening of the secondcavity, then through the second cavity, the distal aperture of thehousing, the first cavity, and to the sensor.

The sensor assembly may be used on any sensor delivery device, such as aguidewire or catheter based systems, for measuring pressure in thearterial system, for example. An example of a one such system, anover-the-wire system described in U.S. Patent Publication Number2010/0234698, the disclosure of which is incorporated herein byreference. One such sensor delivery system is shown in FIGS. 1-3 and 5.The sensor delivery device 10 includes a distal sleeve 20 having aguidewire lumen 22 for slidably receiving a medical guidewire 30. Asensor assembly 100 is coupled to the distal sleeve 20 and includessensor 110 which is capable of sensing and/or measuring a physiologicalparameter of a patient and generating a signal representative of thephysiological parameter, such as pressure. Thus, the distal sleeve 20,and hence, the sensor assembly 100, may be positioned within a patient(e.g., within an anatomical structure of a patient, such as within avein, artery, or other blood vessel, or across a heart valve, forexample) by causing the distal sleeve 20 to slide over the medicalguidewire 30 to the desired position.

The sensor delivery device 10 of FIG. 1 also includes a proximal portion50, which is coupled to the distal sleeve 20. The proximal portion 50includes a communication channel for communicating the signal from thesensor 110 to a location outside of the patient (e.g., to a processor,display, computer, monitor, or to another medical device). Communicationchannel may comprise a fiber optic communication channel in certainpreferred embodiments, such as where the sensor 110 is a fiber opticpressure sensor. Alternately, communication channel may comprise anelectrically conductive medium, such as one or more electricalconducting wires. Of course, many other forms of communication media maybe suitable for transmitting the signal generated by sensor 110 to alocation outside of the patient. In some embodiments, the communicationchannel may comprise any of a variety of fluid and/or non-fluidcommunication media, such as a wireless communication link, or aninfrared capability, or acoustic communications such as ultrasound, aspossible examples.

The proximal portion 50 is also adapted to assist an operator (e.g., aphysician or other medical staff) in positioning the distal sleeve 20and the sensor assembly 100 within an anatomical (e.g., vascular)structure of the patient. This may be accomplished by an operator firstinserting a “standard” medical guidewire 30 into a patient's vasculatureand advancing it past an area of interest. The sensor delivery device 10is then deployed by “threading” the distal sleeve 20 onto the guidewire30 such that the lumen 22 slides over the guidewire 30, and advancingthe distal sleeve 20 (and the associated sensor assembly 100) by moving(e.g., pushing and/or pulling) the proximal portion 50 until sensor 110is in the desired location.

In certain embodiments, the size or “footprint” (e.g., the width and/orthe cross-sectional area) of device 10 may allow it to fit withincertain standard sized guiding catheters. In certain embodiments, thedistal sleeve 20 of the device may be substantially concentric with theguidewire 30. The coupling of the proximal portion 50 to the distalsleeve 20 allows the guidewire 30 to separate from the rest of device 10(e.g., in what is sometimes referred to as a “monorail” catheterconfiguration).

In the embodiments shown, the sensor assembly 100 is coupled to theouter surface of the distal sleeve 20, at or near the distal end of thedistal sleeve 20. Some embodiments may also include a second sensorassembly (not shown), which may be coupled to the outer surface of thedistal sleeve 20 at a more proximal location. The sensor 110 within thesensor assembly 100 may be adapted to measure a physiological parameterof a patient, such as a blood parameter (e.g., blood pressure, bloodflow rate, temperature, pH, blood oxygen saturation levels, etc.), andgenerate a signal representative of the physiological parameter. Theproximal portion 50 which may be coupled to the distal sleeve 20includes a communication channel for communicating the physiologicalsignal from the sensor 110 to a location outside of the patient (e.g.,to a processor, display, computer, monitor, or to another medicaldevice). The proximal portion 50 may preferably be formed of a materialof sufficient stiffness in order to assist an operator (e.g., aphysician or other medical staff) in positioning the distal sleeve 20and the sensor assembly 100 within an anatomical (e.g., vascular)structure of the patient. Depending on the application, the proximalportion 50 (sometimes also referred to as the “delivery tube”) may bestiffer and more rigid than the distal sleeve 20 in order to provide areasonable amount of control to push, pull and otherwise maneuver thedevice to a physiological location of interest within the patient.Suitable materials for proximal portion 50 include a stainless steelhypotube as well as materials such as nitinol, nylon, and plastic, forexample, or composites of multiple materials.

The communication channel may be disposed along an outer surface ofproximal portion 50, or may be formed within the proximal portion 50.For example, communication channel may comprise a communication lumenthat extends longitudinally through proximal portion 50 in someembodiments. Communication channel may comprise a fiber opticcommunication channel in certain embodiments, such as where the sensor110 is a fiber optic pressure sensor. Alternately, communication channelmay comprise an electrically conductive medium, such as electricalconducting wires, or other communication media suitable for transmittingthe signal generated by sensor 110. In some embodiments, thecommunication channel comprises a non-fluid communication medium. Thecommunication channel (e.g., a fiber optic cable) may extend distallybeyond proximal portion 50 to be coupled to sensor 110 on the distalsleeve. In the embodiment shown, the communication channel 60 extendsalong the exterior surface of the distal sleeve 20 and into the sensorassembly 100.

Some embodiments the sensor delivery device 10 may include a secondsensor assembly which may be coupled to the device 10. For example, asecond sensor assembly may be coupled to the proximal portion 50 ordistal sleeve 20 such that the first and second sensor are spaced apartsufficiently (e.g., a fixed distance apart) to span a stenotic lesion.This embodiment may offer the ability to measure fractional flow reserve(FFR) without having to reposition device 10, since once sensor could beplaced distal of the stenotic lesion to measure pressure distal to thelesion (P_(d)), and the other sensor could be placed proximal of thestenotic lesion to measure pressure distal to the lesion (P_(p)). Insome embodiments, the second sensor assembly includes some or all of thevarious features of the sensor assembly 100 discussed herein.

The sensor assembly 100 described herein may also be used with otherpressure sensing systems. For example, while guidewire pressure sensorssystems such as the St. Jude Medical Radi System Pressurewire® Certusand Analyzer typically include a strain gauge type sensor, a fiber opticpressure sensor assembly could be used alternatively, along with anoptical fiber replacing the electrical conductor typically used in suchsystems.

A close up perspective view of the sensor assembly 100 on a distalsleeve 20 is shown in FIG. 2, while a longitudinal cross sectional viewis shown in FIG. 3. The sensor 110 is located within the housing 120,near the distal end 122 of the housing 120 but separated from the distalend 122 by the first cavity 130. In the embodiment shown, the sensor 110is a fiber optic pressure sensor adapted to measure blood pressure.

Various embodiments are particularly useful with fiber optic pressuresensors, though they are not limited to such sensors. An example of afiber optic pressure sensor which may be used in various embodiments isa Fabry-Perot fiber optic pressure sensor, which is a commerciallyavailable sensor. Examples of Fabry-Perot fiber optic sensors are the“OPP-M” MEMS-based fiber optic pressure sensor (400 micron size)manufactured by Opsens (Quebec, Canada), and the “FOP-MIV” sensor (515micron size or 260 micron size) manufactured by Fiso Technologies, Inc.(Quebec, Canada). In certain alternate embodiments, the sensor orsensors 110 may be piezo-resistive pressure sensors (e.g., a MEMSpiezo-resistive pressure sensor), and in other embodiments, the sensoror sensors 110 may be capacitive pressure sensors (e.g., a MEMScapacitive pressure sensor). A pressure sensing range from about −50 mmHg to about +300 mm Hg (relative to atmospheric pressure) may be usedfor making most physiological measurements with sensor 110, for example.

In embodiments using the Fabry-Perot fiber optic pressure sensor as thesensor 110, such a sensor works by having a reflective diaphragm thatvaries a cavity length measurement according to the pressure against thediaphragm. Coherent light from a light source travels down the fiber andcrosses a small cavity at the sensor end. The reflective diaphragmreflects a portion of the light signal back into the fiber. Thereflected light travels back through the fiber to a detector at thelight source end of the fiber. The two light waves, the source light andreflected light travel in opposite directions and interfere with eachother. The amount of interference will vary depending on the cavitylength. The cavity length will change as the diaphragm deflects underpressure. The amount of interference is registered by a fringe patterndetector.

Because such sensors function by transmitting light through the opticalfiber and reflecting the light from the diaphragm, the optical fiber isnormally perpendicular to the diaphragm. Because the optical fiberextends longitudinally along the sensor delivery device, the result isthat the diaphragm of the sensor is perpendicular to the longitudinalaxis of the sensor delivery device. Such an orientation of the sensor,with the diaphragm facing distally and perpendicular to the direction ofmovement of the delivery device through the vasculature, has thepotential to interfere with the movement of the delivery device to thedesired location for making measurements. Various embodiments thereforereduce or eliminate this interference through the use of the filler,while still providing accurate pressure measurements through the use ofcavities and apertures as described herein.

The sensor 110 is encased within a housing 120 which may be alongitudinally extending hollow member which may surround and protectthe sensor 110. The housing 120 may be comprised of any rigid orsemi-rigid biocompatible material such as stainless steel or polyimide,for example. The housing 120 may be cylindrical or may have a circularor any other cross sectional shape. One or both of the proximal end 124and distal end 122 may be flat (having a planar surface perpendicular tothe longitudinal axis of the housing 120) and may be squared or bluntedor alternatively may tapered. The proximal end 124 includes a proximalaperture 126 to allow passage of the communication channel 60 from thesensor 110 to outside of the housing 120. The housing 120 also includesa distal aperture 128 to allow the sensor 110 to sense physiologicaldata such as pressure. The distal aperture 128 may be in the distal end122 of the housing 120, whether the end 122 is flat or tapered, oralternatively may be on another outer surface of the housing, such as onthe side or top of the housing at or near the sensor and where it canprovide communication with the surrounding environment.

The first cavity 130 is a space which surrounds at least the sensingportion of the sensor, such as the diaphragm of the pressure sensor 110at the distal end 112 of the pressure sensor 110. The distal aperture128 of the housing 120 adjoins the first cavity 130 so that the sensor110 can detect physiological data through the distal aperture 128 andthe first cavity 130. In the embodiment shown, the first cavity 130 isformed by the space in that portion of the housing 120 between thedistal end 112 of the sensor 110 and the distal end 122 of the housing120 where the distal aperture 128 is located.

In order to facilitate movement and placement of the device 10 in theanatomical (e.g., vascular) structure of the patient, the housing 120 issurrounded around its outer walls (except the wall adjoining the distalsleeve 20) by a filler 140 which includes a tapered distal end 142. Theproximal end 144 of the filler 140 may also be tapered. For example, asshown in FIGS. 2 and 3, the distal end 122 of the housing 120 isperpendicular to the longitudinal axis of the housing 120 and the distalsleeve 20 and therefore would be a blunt surface which would createresistance when moved into position in a vascular structure. However, itcan further be seen that filler 140 forms a tapered distal end 142 suchthat the sensor assembly 100 forms a smoother, tapered structure that iseasier to navigate through anatomical (e.g., vascular) structures andpassages in a patient (e.g., it allows the device 10 to slide throughvascular passages such as arterial walls without catching or snagging).In the embodiment shown, housing 120 is tapered at its proximal end 124around the proximal aperture 126, and the filler 140 provides additionaltapering to form a smooth tapered surface down to the distal sleeve 20proximal to the housing 120.

In the embodiment shown, the proximal end 144 of the filler 140 extendsaround the distal sleeve 20 and extends distal to the distal end 22 ofthe distal sleeve 20. In alternative embodiments, the entire length ofthe filler 140 may extend around less or more of the distal sleeve 20(or other structure on which the sensor assembly is located), such asencircling the distal sleeve 20 or other structure along the length ofthe filler 140 or not encircling the distal sleeve 20 or other supportstructure at any portion of the filler 140. In addition, the distal end142 of the filler 140 may alternatively be proximal to the distal end 22of the distal sleeve 20.

The filler 140 includes a cavity which is the second cavity 150. Thesecond cavity 150 extends from the distal aperture 128 of the housing120 to an opening 158 in the outer surface of the filler 140. In theembodiment shown, the longitudinal length of the second cavity 150 isless than the longitudinal length of the aperture 158. The opening 158is located directly distal to, adjacent to, and slightly spaced apartfrom the distal end 122 of the housing 120 in the embodiment shown. Inaddition, the distal end 152 of the second cavity 150 extends distal ofthe distal end 159 of the aperture 158.

The filler 140 may be comprised of a single material or more than onematerial. For example, in some embodiments the filler 140 includes oneor more layers of material. In some embodiments, the filler 140 mayinclude a flowable thermoplastic material such as Pebex® or othersuitable material. The filler 140 acts as a tapered casing or cover onthe housing 120 that forms a smooth ramp-like transition between theoutermost aspect of the housing 120 and the outer surface of the distalsleeve 20.

As shown in FIGS. 4 and 5, the sensor delivery device 10 may alsoinclude an outer layer 70, which may surround the distal sleeve 20 andthe sensor assembly 100 in the form of a cover. The outer layer 70 maybe a thermoplastic material which may be a heat shrunk around thefiller, such as Polyethylene terephthalate (PET). The outer layer 70 maycover only the filler 140, may cover the entire sensor assembly 100 andfiller, or may cover the whole distal portion of the sensor deliverydevice 10 including the distal sleeve 20, the communication channel 60and the sensor assembly 100 by wrapping around outside of thesecomponents. In some embodiments, the second cavity 150 may be formed inthe filler 140 and the outer layer 70 may extend across the opening 158of the second cavity 150. The outer layer 70 may include an aperture 78that may overlie the opening 158 of the second cavity 150 and may be thesame size as and aligned with the opening 158, or may be smaller orlarger than the opening 158 of the second cavity 150. In some suchembodiments, the second cavity 150 is a space that is bounded by thedistal end 122 of the housing 120 including the housing distal aperture128 at the proximal end 154 of the second cavity 150. The outer surfaceof the distal sleeve 20 (or other support surface on which the sensorassembly 100 may be located) may form the inner surface/bottom wall ofthe second cavity 150. The filler 140 may form the side walls and distalwall of the second cavity 150. The outer layer 70 may form the outersurface/top wall of the second cavity 150, which may or may not also bepartly formed by the filler 140. During manufacture, the outer layer 70may be applied to the sensor delivery device 10 and the aperture 78 maybe made in the outer layer after application, such as by cutting,etching, melting, or burning in the aperture at the desired location incommunication with the second cavity 150. Alternatively, the aperture 78may be present in the outer layer 70 before the outer layer 70 isapplied to the sensor delivery device 10, and the aperture 78 may bealigned with the second cavity 150 as desired during manufacture whenthe outer layer 70 is applied to the sensor delivery device 10.

Cross sectional views of the sensor delivery device are shown in FIGS. 4and 5. In FIG. 4, the cross section is through the distal sleeve 20,proximal to the housing 120. In FIG. 5, the cross section transects thehousing 120 and the sensor 110. In FIG. 4, the communication channel 60is shown extending along the outer surface of the distal sleeve 20, anda guidewire 30 is shown within the distal sleeve 20. Both the distalsleeve 20 and the communications channel 60 are surrounded by the outerlayer 70. In FIG. 5, the sensor 110 is shown within the housing 120. Thehousing 120 is abutting the distal sleeve 20, which encloses a guidewire30 as in FIG. 4. The space within the housing 120 and surrounding thesensor 110 is filled with gel 114. The outer layer 70 surrounds thedistal sleeve 20 and the housing 120, with the filler 140 within theouter layer 70 partially surrounding both the housing 120 and the distalsleeve housing 20.

Referring back to FIG. 3, the opening 158 is located on the distaltapered end of the filler 140, while the distal aperture 128 is locatedon the distal end 122 of the housing 120. As a result, while the planein which the distal aperture 128 lies is perpendicular to thelongitudinal axis of housing 120 and distal sleeve 20, the plane inwhich the opening 158 lies is neither parallel to nor perpendicular tothe plane in which the distal aperture lies. Rather, the plane in whichthe opening 158 is located is skewed relative to the plane of the distalaperture, with the angle being determined by the angle of the taperingof the outer surface of the filler 140 at the location of the opening158. In the embodiment shown, the tapering of the filler 140 is verygradual, particularly at the location of the opening 158, such that theouter surface of the filler 140 at the location of the opening 158 isalmost but not quite parallel to the longitudinal axis of the distalsleeve 20 and the housing 120, and is therefore almost but not quiteperpendicular to the plane in which the distal aperture 128 of thehousing 120 is located. In the embodiment shown, the plane in which theopening 158 is located is between about 5 and 10 degrees less thanperpendicular (that is, it is about 80 to about 85 degrees) relative tothe plane in which the distal aperture 128 is located.

By locating the opening in a portion of the filler 140 which is parallelto or nearly parallel to the longitudinal axis of the distal sleeve 20,it may be less likely to become snagged or to interact with or damagetissue as it is maneuvered to a location of interest. As such, the planeof the outer surface of the filler 140 at the location of the opening158 may angle inwardly as it extends distally toward the longitudinalaxis of the distal sleeve 20 and the housing 120 at an angle of betweenabout 45 to 0 degrees, such as between about 30 to 1 degree, or about 25to 5 degrees, or about 5 to 20 degrees relative to the longitudinal axisof distal sleeve 20 and the housing 120. The filler 140 may taperinwardly at a constant angle or the angle may vary as it extendsdistally and may include one or more positions in which it is parallelto the longitudinal axis of the distal sleeve or other supportstructure. The result is that the cross-sectional area (perpendicular tothe longitudinal axis of the distal sleeve 70) of the device 10decreases at a constant or varying rate from where it abuts the distalend of the housing 122 to the distal end of the filler 142, optionallywith one or more plateaus in which the cross-sectional area is stable.

The size of the opening 158 of the second cavity 150 (which may beexpressed in terms of diameter or cross sectional area) as well as thevolume of the second cavity 150 may be important to obtaining accuratepressure measurements. In particular, the pulsatile nature of bloodflow, cycling between a diastolic and systolic pressure can complicatethe pressure measurements, making the size of the opening 158 moreimportant. For example, if the size of the opening 158 is too small,there may be dampening or clipping of the pressure measurements whichmay be caused by air bubbles, for example, which may be due to airmoving from the interior of the second cavity 150 out through theopening 158. The proper size of the second cavity 150 and opening 158must therefore balance the need to avoid trapping air and the needpresent the most tapered profile possible to avoid the cavity beingcaught in stent struts or other hard materials like calcified lesions.

In some embodiments, the length of the opening 158 (from proximal todistal end 159) in the second cavity 150 is less than the length of thesecond cavity 150 from the proximal 154 to distal end. In someembodiments, the opening 158 of the second cavity is distally spacedaway from the distal end 152 of the housing. In some embodiments, thesize of the opening 158 of the second cavity 150 may be between about0.01 mm² and about 1.0 mm², such as between about 0.05 mm² and about 0.5mm² or between about 0.3 mm² and about 1.0 mm², such as between about0.4 mm² and about 0.6 mm². In some embodiments, the volume of the secondcavity 150 may be between about 0.01 mm³ and about 0.25 mm³, such asbetween about 0.04 mm³ and about 0.12 mm³ or between about 0.015 mm³ andabout 0.07 mm³, such as between about 0.02 mm³ and about 0.03 mm³. Insome embodiments, the ratio of the cross sectional area of the apertureof the second cavity to the volume of the second cavity is between about0.1 and about 10, such as between about 0.5 and about 2, or betweenabout 3 and about 5, such as between about 4.2 and about 4.4.

In some embodiments, the inside portion of the housing 120, includingthe first cavity 130 may be filled with a gel 114, such as a siliconedielectric gel. The second cavity 150 may also be filled with a gel.Silicone dielectric gels are often used with solid state sensors toprotect the sensor from the effects of exposure to a fluid medium, forexample. If the first cavity 130 is filled with a gel in front of thesensor diaphragm, and/or if the second cavity 150 is filled with a gel,then foreign material may be less likely to penetrate inside the housing120. The gel may also offer added structural stability to the sensor110, and/or may enhance the pressure-sensing characteristics of thesensor 110. Alternatively, one or both cavities 130, 150 may be vacantspaces into which blood or other fluid may flow during use.Alternatively, one or both cavities 130, 150 may be partially filledwith gel and partially vacant.

In use, a guidewire, with or without a catheter, may be inserted into apatient's body though an incision to access a vascular structure. Theguidewire (and catheter, if present) may then be navigated through thevasculature, such as through the arteries, to a location of interest,such as a location within the coronary arteries in order to evaluate thearteries for the presence of, or the severity of, a stenotic lesion. Ifnot already present, a catheter may then be advanced over the guidewire.In some embodiments, the guidewire itself includes a sensor assemblylocated on the guidewire. In other embodiments, the sensor assembly maybe located on the outer surface of the catheter. In still otherembodiments, the sensor assembly may be located on the outer surface ofa sensor delivery device such as a distal sleeve as described herein,and the sensor delivery device may be delivered to the location ofinterest by sliding the sensor delivery device along the guidewire,optimally within the catheter, if present, and exiting the distal end ofthe catheter at a location proximal to the location of interest suchthat the sensor can make the physiological measurement at the locationof interest. Alternatively, the sensor delivery device may be deliveredto the location of interest without the use of the catheter by placingthe guidewire as described, removing the catheter if present, and thensliding the sensor delivery device along the guidewire.

Once the sensor is positioned at the location of interest, a pressuremeasurement may be taken. The location of interest may be a stenoticlesion, and the pressure measurement may be taken downstream (distal) ofthe stenotic lesion. A pressure measurement may also be taken upstream(proximal) of the stenotic lesion, such by using the same sensor (suchas by repositioning the sensor) or by using a separate (such as asecond) sensor on the same sensor delivery device, such that a first(distal) sensor is located distal to the stenosis and the second(proximal) sensor is located proximal to the stenosis. The proximal anddistal pressure measurements may be used to calculate a fractional flowreserve (FFR), and this calculation may be used by a clinician to decidewhether or not an intervention (such as a placement of a stent) isrequired. Alternatively, the location of interest may be a heart valve,and pressure measurements may be obtained proximal and/or distal to theheart valve to assess the functioning of the heart valve. Other pressuremeasurements may be obtained in other locations to assess for clinicalevaluation.

Sensor assemblies according to various embodiments may be used withpowered injector systems, such as the powered injection system shown inFIG. 6. The powered injector system may be used to perform variousfunctions and, when operable, may be coupled (e.g. by electronic signalcommunication) to a physiological sensor delivery device including asensor assembly, such as the various embodiments of a sensor deliverydevice described above. The powered injection system 200 may be used toinject medical fluid, such as contrast media or saline, into a patientwithin the sterile field during a medical procedure (such as during anangiographic or CT procedure). A physiological sensor delivery deviceincluding a sensor assembly may be coupled to the system 200 and usedwithin the sterile field during a patient procedure. The system 200 mayinclude various components, such as a control panel 202, ahand-controller connection 204, a hand controller 212, a first fluidreservoir 206, tubing 208, a pump 210, a pressure transducer 218, asecond fluid reservoir 214, an injection syringe 216, high pressureinjection tubing 222, a valve 220, an air detector 224, and a stopcock226. In some embodiments, the injection syringe 216 (along with itsassociated plunger), which is a pumping device, may be replaced withanother form of pumping device that delivers high-pressure fluidinjections to a patient and may be capable of operating or functioningin different, or multiple, operational modes.

The foregoing description addresses examples encompassing the principlesof various embodiments. The embodiments may be changed, modified and/orimplemented using various types of arrangements. In particular, one ormore embodiments may be combined in a single inlet valve system. Thoseskilled in the art will readily recognize various modifications andchanges that may be made to these embodiments without strictly followingthe exemplary embodiments and applications illustrated and describedherein. Accordingly, it is not intended that the invention be limited,except as by the appended claims.

The invention claimed is:
 1. A sensor delivery device for monitoring afluid pressure within a vascular structure of a patient, the sensordelivery device comprising: an elongated tubular sheath sized forsliding along a guidewire, the sheath having an outer surface; a sensorassembly comprising: a fiber optic sensor; a housing surrounding thesensor, the housing comprising a proximal end having a proximalaperture, a distal end having a distal aperture, an inner surfaceadjoined to the outer surface of the sheath, and an outer surfaceopposing the inner surface; a first cavity between a distal end of thesensor and the distal aperture of the housing; a filler on the outersurface of the housing extending at least distally from the distal endof the housing, the filler having an outer surface that tapers inwardtoward the outer surface of the sheath as the filler extends distally; asecond cavity, the second cavity located in the filler, the secondcavity comprising an opening at the outer surface of the filler, thesecond cavity adjoining the distal aperture of the housing; an opticalfiber extending along the outer surface of the sheath, passing throughthe proximal aperture of the housing and adjoined to the sensor at adistal end of the optical fiber.
 2. The sensor delivery device of claim1 further comprising an outer layer overlying the filler and comprisingan aperture, wherein the outer layer partially covers the second cavityand wherein the aperture overlies the opening of the second cavity. 3.The sensor delivery device of claim 2 wherein the outer layer encirclesthe sensor assembly, the sheath, and the optical fiber.
 4. The sensordelivery device of claim 2 wherein the outer surface of the sheath formsa bottom of the second cavity, wherein the distal end of the housingforms a proximal end of the second cavity, wherein the filler forms adistal end of the second cavity and opposing side surfaces of the secondcavity, and wherein the outer layer forms a top of the second cavity. 5.The sensor delivery device of claim 1 wherein the sensor comprises apressure sensor.
 6. The sensor delivery device of claim 5 wherein thefiller surrounds all of the housing.
 7. The sensor delivery device ofclaim 6 wherein the filler extends proximally from the proximal end andouter surface of the housing and tapers inwardly toward the outersurface of the sheath as it extends proximally.
 8. The sensor deliverydevice of claim 1 wherein the second cavity has a length from a proximalto a distal end of the second cavity which is greater than a length ofthe outer layer aperture from a proximal to a distal end of the outerlayer aperture.
 9. The sensor delivery device of claim 1 wherein theouter layer aperture has an area of between 0.01 and 1.0 mm².
 10. Thesensor delivery device of claim 9 wherein the second cavity has a volumeof between 0.01 and about 025 mm³.
 11. The sensor delivery device ofclaim 1 wherein the sheath comprises a distal sleeve, the sensordelivery device further comprising a proximal portion adjoined to thedistal sleeve, wherein the optical fiber extends within the proximalportion and wherein the proximal portion is configured to be separatefrom the guidewire.
 12. The sensor delivery device of claim 1 whereinthe opening in the filler is skewed relative to the distal aperture ofthe housing and is skewed relative to a longitudinal axis of the sheath.13. A sensor delivery device for monitoring a fluid pressure within avascular structure of a patient, the sensor delivery device comprising:an elongated tubular sheath sized for sliding along a guidewire, thesheath having an outer surface; a sensor assembly comprising: a fiberoptic pressure sensor; a housing surrounding the sensor, the housingcomprising a proximal end having a proximal aperture, a distal endhaving a distal aperture, an inner surface adjoined to the outer surfaceof the sheath, and an outer surface opposing the inner surface; a firstcavity between a distal end of the sensor and the distal aperture of thehousing; a filler on the outer surface of the housing extending at leastdistally from the distal end of the housing, the filler having an outersurface that tapers inward toward the outer surface of the sheath as thefiller extends distally; a second cavity, the second cavity located inthe filler, the second cavity comprising an opening at the outer surfaceof the filler, the second cavity adjoining the distal aperture of thehousing; an optical fiber extending along the outer surface of thesheath; an outer layer encircling the sensor assembly, sheath andoptical fiber and comprising an aperture, wherein the outer layerpartially covers the second cavity and wherein the aperture overlies theopening of the second cavity.
 14. The sensor delivery device of claim 13wherein the outer surface of the sheath forms a bottom of the secondcavity, wherein the distal end of the housing forms a proximal end ofthe second cavity, wherein the filler forms a distal end of the secondcavity and opposing side surfaces of the second cavity, and wherein theouter layer forms a top of the second cavity.
 15. The sensor deliverydevice of claim 13 wherein the filler surrounds all of the housing andextends proximally from the proximal end and outer surface of thehousing and tapers inwardly toward the outer surface of the sheath as itextends proximally.
 16. The sensor delivery device of claim 13 whereinthe second cavity has a length from a proximal to a distal end of thesecond cavity which is greater than a length of the outer layer aperturefrom a proximal to a distal end of the outer layer aperture.
 17. Thesensor delivery device of claim 13 wherein the outer layer aperture hasan area of between 0.01 and 1.0 mm².
 18. The sensor delivery device ofclaim 17 wherein the second cavity has a volume of between 0.01 and 0.25mm³.
 19. The sensor delivery device of claim 13 wherein the sheathcomprises a distal sleeve, the sensor delivery device further comprisinga proximal portion adjoined to the distal sleeve, wherein the opticalfiber extends within the proximal portion and wherein the proximalportion is configured to be separate from the guidewire.
 20. The sensordelivery device of claim 13 wherein the aperture of the outer layer isskewed relative to the distal aperture of the housing and is skewedrelative to a longitudinal axis of the sheath.
 21. A method of measuringintravascular pressure in a patient at a location of interestcomprising: inserting a sensor delivery device into the patient'svasculature, the sensor delivery device comprising: an elongated tubularsheath sized for sliding along a guidewire, the sheath having an outersurface; a sensor assembly comprising: a fiber optic sensor; a housingsurrounding the sensor, the housing comprising a proximal end having aproximal aperture, a distal end having a distal aperture, an innersurface adjoined to the outer surface of the sheath, and an outersurface opposing the inner surface; a first cavity between a distal endof the sensor and the distal aperture of the housing; a filler on theouter surface of the housing extending at least distally from the distalend of the housing, the filler having an outer surface that tapersinward toward the outer surface of the sheath as the filler extendsdistally; a second cavity, the second cavity located in the filler, thesecond cavity comprising an opening at the outer surface of the filler,the second cavity adjoining the distal aperture of the housing; and anoptical fiber extending along the outer surface of the sheath, passingthrough the proximal aperture of the housing and adjoined to the sensorat a distal end of the optical fiber; advancing the sensor deliverydevice to the location of interest; and measuring the intravascularpressure at the location of interest using the pressure sensor.
 22. Thesensor delivery device of claim 21 wherein the outer layer aperture hasan area of between 0.01 and 1.0 mm² and wherein the second cavity has avolume of between 0.01 and 0.25 mm³.